1. Field of the Art
This invention relates to an endoscope for medical use, incorporating an objective lens drive mechanism in association with an optical objective lens system on its insertion instrument, and more particularly to an endoscope with an objective lens drive mechanism permitting to shift the position of at least one lens element of an optical objective lens system in the direction of its optical axis by remote control to vary at least observation depth, image magnification scale or view field angle.
2. Prior Art
In general, endoscopes which are used for medical purposes are largely constituted by a manipulating head assembly to be gripped by an operator to control the operation of the endoscope, an insertion instrument extended out on the front side of the manipulating head assembly for insertion into a body cavity, and a universal cable led out from the manipulating head assembly for connection to a light source. In terms of construction and function, the insertion instrument is composed of a rigid tip end section, an angle section and a flexible rod section, from its fore distal end to proximal end. The flexible rod section, which occupies a major portion of the entire length of the insertion instrument, is arranged to be flexible in arbitrary directions along a path of insertion which may contain bends. The rigid tip end section is provided with at least an illumination window and an observation window, along with an outlet opening of a biopsy instrument channel which is usually provided in the insertion instrument for the purpose of insertion of forceps or other instruments. The angle section is flexible by remote control from the side of the manipulating head assembly. Accordingly, the rigid tip end section can be turned into an arbitrary direction by bending the angle section by remote control.
A light emitting end of a light guide, which consists of a bundle of fiber optics, is disposed in the illumination window on the rigid tip end section of the insertion instrument. The light guide is passed through the insertion instrument and assembled into the universal cable which is led out from the manipulating head assembly as mentioned above. Further, an objective lens system is mounted on an image pickup assembly block within the rigid tip end section of the insertion instrument, along with a solid-state image sensor device which is located at the focus of the objective lens system. Normally, the image pickup assembly block is located substantially at a central position in a cross-sectional area of the rigid tip end section. On the other hand, it is usually the case that an illumination window is provided at one or a plural number of positions in the vicinity of an observation window at the distal end of the image pickup assembly block. Accordingly, the center of observation view field is located substantially at a central position of the insertion instrument, and the illumination window or windows are arranged to irradiate the entire view field including center portions thereof.
The optical objective lens system of the endoscopic image pickup is normally constituted by an objective lens group which is composed of a plural number of lens elements. Preferably, the objective lens group should be able to vary at least the depth of focus, image magnification rate or view field angle depending upon the location of an observation site or the purpose of examination. In this regard, it has thus far been known in the art to arrange one or a plural number of lens elements of an objective lens group to be movable in the direction of optical axis of the objective lens system. For this purpose, an objective lens group is usually mounted on a lens frame which is constituted by a fixed lens frame and a movable lens frame. The movable lens frame is slidably fitted in the fixed lens frame which functions as a guide when the movable lens frame is moved in the direction of optical axis.
Accordingly, the optical objective lens system necessarily includes a drive means for moving the movable lens frame in the direction of optical axis. As for drive means of this sort, for example, there have been proposed a diversity of drives using piezoelectric elements, shape memory alloys, artificial muscle and the like. However, normally a proximal end of a control cable which is connected to a movable lens frame is extended into the manipulating head assembly of the endoscope thereby permitting to shift the position of a movable lens or lenses in the direction of the optical axis by remote control. The movable lens is moved between a fore position closer to the subject side and a rear position closer to the imaging side. Location of the movable lens in the rear position gives a smaller image magnification rate and a greater focal depth. On the other hand, location of the movable lens in the fore position gives a greater image magnification rate and a smaller focal depth. Accordingly, in this case, the operator can shift the position of the movable lens by driving same through the control cable or other suitable transmission member, depending upon the location of an intracavitary portion under examination or the nature of examination. This shift of the movable lens position is feasible even when the insertion instrument of the endoscope is inserted in a body cavity of a patient.
In order to pick up clear images through an optical objective lens system, a movable lens has to be located precisely in either one of the above-mentioned fore and rear positions. This is so especially when a movable lens is located in a fore position on the side of a subject because the focal depth is shallow in the fore position and therefore a slight deviation from a predetermined position will invite considerable deteriorations in quality of picture images. It follows that a movable lens should be positioned correctly at least when shifted to a fore position on the side of a subject. For remote-controlling a movable lens, a control cable is connected to a movable lens frame as mentioned above. Various forms of remote control cables of this sort have been known in the art, for example, from Japanese Laid-Open Patent Specification H4-13112 and Japanese Utility Model Publication S55-55041.
Disclosed in Japanese Laid-Open Patent Specification H4-13112 is a lens group consisting of a front group lens, a rear group lens and a magnification control lens which is movable in the direction of optical axis. The magnification control lens is arranged to slide along a slide member which is provided between front and rear lens frame which support the front and rear lens groups, respectively. The magnification control lens itself is fitted in a magnification lens frame, and an operating wire is connected to the magnification lens frame thereby to permit to move the latter back and forth by remote control from the manipulating head assembly. The operating wire is passed through and fixedly connected at its fore end to a wire threading member which is provided integrally with the rear group lens frame. The other end of the operating wire is connected to a solenoid which is energizable to shift the magnification control lens between a fore position on the side of the front group lens and a rear position on the side of the rear group lens. The control cable of this sort can be referred to as a push-pull type.
Disclosed in Japanese Utility Model Publication S55-55041 is an endoscope employing an image guide in such a way as to vary the distance between a light incident or input end of the light guide and an optical objective lens system. In this particular prior art, the image guide is moved by the use of a control cable. More particularly, in this case, a projection is provided on a mouth piece which is fitted around a fore end portion of an image guide, and a screw shaft threaded into the projection to connect thereto one end of a wire which is passed through a coil tube. In this case, the position of the light input end of the image guide is adjusted by rotating the wire about the longitudinal axis within the coil tube. The control cable of this sort can be referred to as a rotating type.
Of the above-mentioned two types of control cables, the push-pull type can produce a sufficient driving force through the operating wire when the wire is pulled but not when the wire is pushed. Therefore, it becomes necessary to provide a biasing means at the fore end of the operating wire for biasing the multiplication control lens toward the front group lens. The control cable of this type has another problem that, after repeated operations, the operating wire can get elongated to cause variations in pulling stroke length. On the other hand, the rotating type control cable also has inherent drawbacks that its wire easily gets twisted and fails to transmit rotation smoothly to its fore end, and, gets elongated after repeated use similarly to the above-mentioned push-pull type.
Further, disclosed in EP 0 420 057 is an endoscopic objective lens drive mechanism employing a screw rod for driving a movable lens, connecting the screw rod to a movable lens frame through a nut member which is in threaded engagement with the screw rod. A flexible transmission shaft is connected to the screw rod, and, upon turning a proximal end of the flexible transmission shaft, the screw rod is rotated by remote control to translate the nut member in direction parallel with the optical axis of an objective lens system.
In this connection, an angle section which is provided on the proximal side of a rigid tip end section of an endoscopic insertion instrument is built into a flexibly bendable structure for the purpose of angularly turning or bending the rigid tip end section into arbitrary directions by remote control. The angle section is flexibly bendable at least in upward and downward directions and normally bendable in four directions, i.e., in upward, downward, rightward and leftward directions. For this purpose, a pair of upper and lower operating wires are connected to the angle section at upper and lower positions, while a pair of right and left operating wires are connected to the angle section at right and left positions. By pulling one of the upper and lower operating wires while feeding forward the other wire, the angle section is angularly bent either in an upward or downward direction. Similarly, by pulling one of the right and left operating wires while feeding forward the other wire, the angle section is angularly bent either in a rightward or leftward direction. In some cases, the angle section is arranged to have the same maximum bending angle in the respective bending directions. However, in this regard, it has been the general practice to arrange the angle section such that it is bendable through a larger angle in an upward direction, and actually the angle section is more frequently bent in upward directions in use.
The above-described bending operation on the angle section should be as light as possible in operating load, and at the same time should be able to bend the angle section toward an aimed direction. Various component parts which are threaded through the angle section can be a load which acts against bending operations. In this regard, a biopsy channel, which is usually provided on an endoscope for insertion of forceps or other instruments, imposes the greatest resistance to a bending operation. In addition, the flexible transmission shaft is also a great resistance to flexures in bending directions. On the other hand, the light guide and the signal cable which is connected to a solid-state image sensor device can be bent relatively easily. Therefore, depending upon the positions of relatively hardly bendable component parts and relatively easily bendable component parts in the angle section, maneuverability of the angle section can be disabled at the time of turning the angle section to a certain direction, e.g., by an extremely large load which exists in that particular direction or due to twisted movements of the angle section.
In view of the foregoing situations, it is an object of the present invention to improve maneuverability in flexibly bending an angle section of an endoscopic insertion instrument with an endoscopic objective lens drive mechanism having a lens drive shaft for displacing a movable lens of an objective lens system in the direction of its optical axis, and a flexible transmission shaft as a control cable for rotationally driving the lens drive shaft by remote control.
It is another object of the present invention to provide an endoscope with an objective lens drive mechanism, having a control cable of the objective lens drive mechanism and a biopsy channel rationally positioned within an angle section of an endoscopic insertion instrument, uniformly distributing loads in all directions of bending operations on the angle section to permit an operator to bend the angle section of the endoscopic insertion instrument smoothly and accurately toward an aimed direction.
It is still another object of the present invention to provide an endoscope with an objective lens drive, which is so arranged to bend an angle section of an endoscopic insertion instrument through a maximum angle particularly in an upward direction and to lessen a load against upward bending operations on the angle section.
According to the present invention, in order to achieve the above-stated objectives, there is provided an endoscope with an objective lens drive mechanism, comprising: an insertion instrument having an elongated flexible body with an angle section and a rigid tip end section successively connected to a fore end of the flexible body, the angle section being flexible bendable for turning the rigid tip end section at least in upward and downward directions; an image pickup assembly unit of an objective lens system accommodated within a casing of the rigid tip end section with an observation window along with an illumination window and an exit opening of a biopsy channel, the optical objective lens system including at least a fixed lens mounted on a fixed lens frame and at least a movable lens mounted on a movable lens frame; and an objective lens drive mechanism including a lens drive shaft rotatably mounted within the casing of the rigid tip end section, a flexible transmission shaft connected between the lens drive shaft and a rotational drive source, and an offset arm extended out from the movable lens frame and engaged with the lens drive shaft through a translating mechanism for converting forward and reverse rotations of the lens drive shaft into linear back and forth movement of the movable lens frame; interior of the casing of the rigid tip end section being divided into right and left subsections along a center line of upward and downward flexures of the angle section for the purpose of laying out internal components, the observation window being located across the flexural center line to occupy part of both of the right and left subsections, the exit opening of the biopsy channel being located in one of the right and left subsections, and the lens drive shaft of the objective lens drive mechanism being located in the other one of the right and left subsections away from the exit opening of the biopsy channel.
In this instance, in a case where the angle section is adapted to be flexibly bendable in upward and downward direction by pulling and pushing a pair of upper and lower operating wires which are connected in the angle section, a center line of upward and downward flexure of the angle section corresponds to a line which connects the upper and lower operating wires in a plane perpendicularly intersecting the longitudinal axis of the angle section. By way of the center line of upward and downward flexures, the interior of the rigid tip end section is divided into right and left semi-circular subsections for laying out internal component parts. Further, in a case where the angle section is adapted to be flexibly bendable also in rightward and leftward directions by pulling and pushing a pair of right and left operating wires which are connected to the angle section, the interior of the rigid tip end section can also be similarly divided into upper and lower subsections by way of a center line of rightward and leftward flexures of the angle section for laying out internal component parts. Accordingly, the internal space of the rigid tip end section can be divided into four subsections in total, which are each shifted by 90 degrees from an adjacent subsection.
Any way, the lens drive shaft and the exit opening of the biopsy channel are located separately in the right and left subsections, respectively. In a case where the interior of the rigid tip end section is divided into four subsections and the lens drive shaft is located in one of lower (or upper) subsections, the exit opening of the biopsy channel is located in the other one of the lower (or upper) subsections away from the lens drive shaft. Further, in a case where the lens drive shaft and the exit opening of the biopsy channel are located in lower (or upper) subsections, a light guide which is connected to an illumination window is located in one of or in each one of upper (or lower) subsections. The movable lens frame is connected to the lens drive shaft through a translating means and an offset arm. Accordingly, by setting the offset arm in a suitable direction and length, the lens drive shaft which drives the movable lens frame can be located rationally within the rigid tip end section with respect to the position of the exit opening of the biopsy channel and irrespective of the position of the movable lens frame. Upon determining the positions of the lens drive shaft and the exit opening of the biopsy channel in this manner, the positional relations between the control cable and the biopsy channel, especially their positional relations within the angle section which is directly connected to the proximal end of the rigid tip end section are determined accordingly.
It is desirable that the observation window on an end face of a casing of the rigid tip end section be located at a position which is as close as possible to the center of the end face. For this purpose, it is the general practice to provide the exit opening of the biopsy channel under the observation window and at a position which is slightly deviated to the right or left of the observation window. Consequently, from the standpoint of maneuverability of the angle section in its bending operations and also from the standpoint of effective use of internal space of the angle section, it is desirable to locate the lens drive shaft substantially in a symmetrical position with respect to the center line of upward and downward flexures of the angle section.
By setting the lens drive shaft and the exit opening of the biopsy channel in the above-described positional relations, it becomes possible to retain the control cable, which is connected to the lens drive shaft, and the biopsy channel, which is extended to the exit opening, in such positional relations as would not impede flexural bending movements of the angle section. For this purpose, a spacer member is fitted in the angle section to divide the interior of the latter into four subsections, thereby retaining internal components separately in the respective predetermined positions. The maneuverability of the angle section can be improved furthermore in a case where the control cable and the biopsy channel are retained separately in the respective positions by the use of the spacer member.
As for an example of the translating means for converting rotations of the lens drive shaft into linear movements of the movable lens frame, there may be employed a combination of a screw rod which is connected to the lens drive shaft, and a nut member which is provided at the distal end of the offset arm and held in threaded engagement with the screw rod. Alternatively, there may be employed a combination of a cam member which is connected to the lens drive shaft, and a cam pin which is provided on the side of the offset arm of the movable lens frame and held in engagement with a cam groove on the cam member. The objective lens system may contain a single movable lens frame or a plural number of movable lens frames. In this connection, it is desirable to employ a cam mechanism in the case of an objective lens system with a plural number of movable lens frames. Further, for the sake of compactness of the objective lens system, it is preferably to provide a guide surface on an interior surface of the fixed lens frame thereby to guide sliding movements of the movable lens frame, and to provide a slot in the fixed lens frame for passing the offset arm of the movable lens frame.
The above and other objects, features and advantages of the present invention will become apparent from the following particular description, taken in conjunction with the accompanying drawings which show by way of example some preferred embodiments of the present invention.